Dry eye (e.g., keratoconjunctivitis sicca), can be diagnosed pathologically during ophthalmic exams as superficial punctate keratopathy (SPK) of the ocular surface epithelium. It is a common and symptomatic condition which is especially prevalent in post-menopausal women. Dry eye is defined as an abnormal state in the amount and quality of tears, and in many cases, results in insufficient tears in any one of the lipid layer, the aqueous layer and the mucin layer, thereby causing keratoconjunctivitis disorder. This condition can induce various ocular surface problems of varying degrees such as foreign body sensations, burning sensations, and damage of visual acuity in severe cases due to the damage of the conjunctiva and cornea. This includes recurrent corneal ulceration with resultant corneal scarring.
Disorders such as reduced shedding of tears, tear deficiency, dry eye syndrome, Sjogren's syndrome, keratoconjunctivitis sicca, Stevens-Johnson syndrome, ocular pemphigus, marginal blepharitis, failure of eyelid closure, sensory nerve injury, exposure keratopathy, corneal ulcers, corneal scarring, etc. are included in the category of dry eye.
One of the most common treatments of dry eye is to use an ocular instillation of artificial tears at the time when dry eye symptoms occur to temporarily supplement and stabilize the tear film. These artificial tears, which contain viscoelastic materials such as methyl cellulose, chondroitin sulfate, and hyaluronic acid, are commonly applied to the eyes as a substitute for lipid, aqueous and mucin. However, since the artificial tears are physically and physiologically different from mucin, the therapeutic effect is limited.
Another common method to treat dry eye is to use a cyclosporine A composition which is normally used as a therapeutic agent for increasing tear secretion through stabilizing the epithelial cells and increasing goblet cells in the dry eyes. Because cyclosporin A inhibits the function of helper T cells through inhibiting the formation of interleukin-2 (one of the major inflammatory cytokines), which results in reducing lymphocytic infiltration of the lacrimal gland, thereby increasing tear production, the cyclosporin A is used as an agent for treating dry eye diseases.
However, while these treatments may provide results for dry eye, they also, depending on their viscosity, can cause blurring of vision when the viscosity of the composition is high. For example, higher viscosity products are used for more severe forms of dry eye but because these products can cause blurry conditions, they are not an ideal treatment. On the other hand, compositions with a lower viscosity are not viscous enough and are less effective when used as a lubricant.
Further, while these treatments provide temporary relief and/or increase tear secretion to the eye, these treatments are often difficult to administer. Eye treatment solutions are normally self-administered by using either an eye cup or a dropper. The rim of the eye cup is configured to tightly engage against the soft tissue surrounding the eye. Because of the eye cup rim's mating anatomical design, the rim forms a positive seal when placed over the eye and gently presses against the infra-orbital tissue. A liquid such as an eye wash solution is then placed in the eye cup and the cup is held against the infra-orbital tissue of the eye. The head is tilted back to allow the solution to immerse the eye. The head may also be moved from side to side to allow the solution to be fully distributed over the cornea and the peripheral tissues of the eye.
Another popular device for self-administering a fluid to the eye is an eye dropper. The eye drop solution is delivered directly into the eye from either a dropper or a dropper type bottle. The person is usually lying down or has the head leaning back during administration. When using the dropper method of administration, one hand of the user pulls the lower lid away from the eye to expose the conjunctiva so that one or more drops of the solution can be introduced.
While most people can manage either the eye cup immersion or the eye drop method for the self-administration of a fluid to the eye, there is a segment of the population which find these devices and methods awkward or difficult to perform because of various visual and/or physical limitations. For example, individuals having partial or impaired vision, neuromuscular problems, muscular and/or skeletal disease, tremor due to Parkinson's disease and those lacking hand/wrist coordination would fall into this group. Likewise, elderly patients, the largest group of eye drop users, often have hand-eye coordination problems, tremors or arthritis, affecting the hands and/or the cervical spine, making eye drop administration difficult if not impossible. Many users report that they have trouble keeping track of their regimens and often repeat doses or miss them entirely, suffering potential consequences in either event. Further, pediatric patients and animals often fight such application which typically results in under dosing due to the patient's attempts to prevent the eye drops from being administered, or overdosing, as a result of the administrator's attempt to ensure that sufficient dosage is being applied.
Accordingly, in view of the foregoing limitations and problems discussed above, there is a need for an ophthalmic composition for administration as a spray to the eye which has an improved viscosity, can be used to apply existing treatments, is easy to use and is acceptable to a wide range of users, including those with physical and visual limitations who are unable to self-apply eye products.